With crafting and gathering, it all depends on what you do really. They can also be HUGE money sucks if you don't do them correctly (i.e.-buy all materials on MB instead of gathering your own or asking friends). Even worse when your friends aren't online and you end up buying their materials on the MB (yea... happened to me a few times, but we always refund each other).

Myself, I'm a Culinarian and Fisher, which I think is a great combo. If you add in Botanist too, it's pretty much perfect (but my FC has like, 5 lvl 50+ botanists, sooo I just let them run around). But I can say, people love food. Get a decent level and make some of the higher stuff (heck, even the lower stuff still sells well honestly). I used to sell food on the MB, but lately, my FC has come up with a plan for stockpiling ourselves, but with only 2 CUL doing it and 20+ players... uh, I don't really have the mats or time to spare :P (but there is money to be made there).

Also, shards, crystals, catalysts ALWAYS sell. They are needed for crafter's. People are always crafting. Prices are almost always high due to people selling low but in huge stacks.

Me personally, I like using Fishing for majority of my retainer income. I've found a few fish that just sell on a very constant and stable basis. So I just keep those coming in with my retainer and selling them in small stacks of 3-5 usually. The problem with the Market Boards though is they differ from world to world. In mine, Bluebell Salmon, White Coral, Red Coral, and just about any shark sells nice and high constantly. Bluebell are a bit iffy though. They come and go (like, I won't sell any for a few days, then all of a sudden, people are buying up all of them).